You'll receive this quest automatically at the end of the Prologue.
You won't really have to do a lot for this quest. It's an overview quest, and you'll complete it by completing a series of other quests:
The Salamander's Tail
(Chapter I). You'll learn that the mutagens stolen by the Salamandra were moved to Vizima, and that Azar Javed is the name of the mysterious mage who led the attack on Kaer Morhen.
(Chapter II). While investigating the Salamandra in the
, you'll eventually confront Azar Javed in front of the mage's tower in the
. He won't reveal why he assaulted Kaer Morhen, and he'll defeat you in the battle.
Lock and Key
(Chapter III). You'll take down a trio of Salamandra bases in Vizima without finding anything useful, but then you'll encounter the Professor, and you'll kill him (with the help of a kikimore queen).
(Chapter V). You'll confront and kill Azar Javed during this quest, and you'll learn that the Grand Master of the Order of the Flaming Rose is the one behind everything.
(Epilogue). You'll defeat the Grand Master in the Ice Plains, and when you loot his corpse, you'll finally regain the
Secrets Stolen from Kaer Morhen
, which will complete the quest.